Rebound pug mill

ABSTRACT

A main pug mill or clay mixer has a rebound pug mill adjacent thereto. The rebound pug mill has a trough with an inlet for rebound material and an extruding head at the end of the trough with an outlet discharging into the main pug mill. Paddles in the trough comminute rebound material admitted through the inlet. Paddles in the extruding head extrude comminuted rebound material through the discharge outlet and into the main pug mill, thus to meter rebound material gradually into the main pug mill.

1 51 July 18, 1972 United States Patent Hartley REBOUNDPUGMILL 1,806,139 5/1931 1,871,416 8/1932 Broadfield [72] Inventor. Nelson Hartley, Towson, Md. 2,806,678 9/1957 Stevensm [73] Assignee: Hartley Controls Corporation, Neenah, 2,823,868 2/1958 Scherer......... Wis. 3,182,633 5/1965 Lodige et a1. 3,250,321 5/1966 Root............. [22] 29'1971 3,314,661 4/1967 Franklin... [21] App1.No.: 138,634 3,387,829 6/1968 Primary Examiner-Robert W. Jenkins Attorney-Wheeler, House & Wheeler Related US. Application Data [63] Continuation of Ser. No. 843,628, July 22, 1969,

abandoned.

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UNITED STATES PATENTS 277,319 5/1883 Miller l5 Claim, 5 Drawing figures Patented July 18, 1972 2 Sheets-Sheet 1 Jazzy/0r %elswz glam lg /& 7 40 Patented July 18, 1 972 2 Sheets-Sheet 2 REBOUND PUG MILL CROSS REFERENCE TO RELATED APPLICATION This application is continuation of my copending US. application, Ser. No. 843,628 filed July 22, I969, now abandoned.

BACKGROUND OF THE INVENTION Clay mixed with water, etc., in a pug mill is typically discharged from the pug mill through a screw compressor or the like which de-aerates the mixed clay and delivers it to a station where the clay is formed into bricks, pipe, etc., at a uniform compacted moldable consistency. It is not unusual for something to happen at the molding station to spoil the shape or the ultimate product. Waste material, hereinafter sometimes termed rebound material," is then returned to the pug mill for reprocessing. However, the rebound material which has been compacted and de-aerated does not mix well with fresh material in the pug mill. The mixing tools in the pug mill are designed to work on relatively uncompacted material. Thus the rebound material will usually not be broken up and will not blend smoothly with the fresh material. The rebound material tends to clog the mill, interferes with the blending operations, forms hard spots, etc. Moreover, if there is a heavy return of rebound material dumped into the pug mill all at once, it will overload the pug mill with a heavy concentration of compacted material and possibly jam the pug mill.

SUMMARY OF THE INVENTION The present invention combines with a conventional or main pug mill a separate rebound pug mill which holds rebound material and meters it gradually back into the main pug mill in such a way that a relatively small proportion of the rebound material is present in the output from the main pug mill.

The rebound pug mill also comminutes the rebound material to break it up from a compacted, de-aerated mass into relatively small chunks which will more easily be broken up into still smaller pieces in the main pug mill for smoother and more complete integration with the fresh materials undergoing mixing in the main pug mill. Comminution in the rebound pug mill takes place both in an open trough with cutting blades or paddles and in an extruding head at the end of the trough which has a discharge opening covered with a grill and through which partially comminuted rebound material is extruded to further break up the rebound material and adapt it for processing in the main pug mill.

According to the present invention, the parts of the rebound pug mill which are subject to most intensive wear, namely, the extruding head and the grill, are removably connected to the other parts of the rebound pug mill, thus to simplify removal thereof for repair or replacement.

Other objects, features, and advantages of the invention will appear from the following disclosure.

DESCRIPTION OF DRAWINGS FIG. 1 is a side elevation of apparatus embodying the invention.

FIG. 2 is a cross section taken along the line 2--2 of FIG. 1

FIG. 3 is a cross section taken along the line 33 of FIG. 1.

FIG. 4 is a fragmentary top view of the rebound pug mill portion of the apparatus shown in FIG. 1.

FIG. 5 is a perspective view showing the rebound pug mill mounted to discharge into the main pug mill.

PREFERRED EMBODIMENTS Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structure. The scope of the invention is defined in the claims appended hereto.

Main pug mill 10 is conventional and is not shown in any detail. It will typically contain paddles or a screw to effectuate proper blending and mixing of clay, water, etc. At its discharge, the main pug mill 10 will typically have a compression screw to compress the blended material to the proper molding consistency and to de-aerate the material.

In accordance with the present invention, rebound pug mill 11 is mounted above and at one side of the main pug mill 10. The details of the mounting are not critical. For purposes of i1 lustration, the rebound pug mill 11 is mounted on brackets 12 which may be supported on cross beams 13 or the like.

The rebound pug mill 1] consists of an open top U-shaped trough 14 having a semi-cylindrical bottom wall. One end of the trough I4 is closed by an end wall 15. At its other end trough 14 is provided with an end flange 16 through which the trough 14 opens into an axially extending head or chamber I7. Chamber 17 is removably supported on flange 16 by complementary flange 20 and a peripheral series of releasable fasteners such as bolts 21.

Extruding head 17 consists of a short cylinder having an end flange 22 releasably fastened by a row of bolts 23 to support bracket 12 and to an end plate 24 on which is mounted a bracket 30 which carries a bearing block 25 for the paddle shaft 26. The other end of the trough 14 is provided with a similar plate 24, bracket 30 and bearing block 25 for the other end of the shaft 26. Shaft 26 may be driven from motor 27 through belt 28 to a pulley 29 on the end of shaft 26.

Paddle shaft 26 carries a number of paddles 32, each of which typically consists of a nonskewed cutting blade 33 projecting radially outwardly from the shaft 26. At the outboard end of each paddle 33 there is a cap 34. Cap 34 is curved circumferentially on an are complementary to the curved bottom wall of the trough 14 and the cylinder wall 17 of the extruding head.

The blades 33 are disposed at a right angle to the longitudinal axis of the trough. Accordingly, they are not twisted or skewed and are thus not relied upon to impart to the rebound material any movement axially of the trough. The leading edges of the blades 33 are desirably made of hardened material. These edges slice the rebound material into small pieces. Flow of rebound material along the trough is primarily by gravity.

The rebound material is admitted to the trough 14 through cubical hopper 35 which is desirably disposed over the inlet end of the trough 14 and is cubical or box-like in configuration with straight, non-tapered walls. The hopper 35 has sufficient volume to hold an ample quantity of rebound material as it is returned from the molding stations.

Shaft 26 extends through trough 14 and through the extruding head 17. Paddles 32 are substantially equally spaced along the shaft 26 both in the trough 14 and in the extruding head 17.

In the disclosed embodiment, there are three longitudinally extending rows of paddles 32. Each row is wound helieally about the axis of the shaft 26, thus to displace successive paddles in each row arcuately around the shaft from one paddle to the next.

The side wall of the extruding head 17 is provided with an opening 36 at its side above the main pug mill or mixer 10. Opening 36 is partially closed by a grillwork 37 which consists of a series of curved cutting bars 40, the ends of which are fastened as by welding to cross mounting bars 41. The wrap wall of the extruding head 17 is provided at the ends of opening 36 with upstanding flanges 42. The cross mounting bars 41 of grillwork 37 are releasably attached to these flanges 42 by fasteners such as bolts 43.

The curved grill bars 40 are desirably spaced apart on about two inch centers. The caps 34 of the paddles 32 which are inside of the extruding head 17 sweep past the grill 37 and will extrude or press comminuted rebound material through the spaces between the bars 40 and will discharge the same on the path of the arrows 44 into the main mixer 10. Passage of the rebound material through the grillwork 37 insures that no piece will exceed in size the spacing between bars 40.

The extruding chamber 17 is closed over its top, thus to build up extruding pressure therewithin.

The caps 34 of the paddles have the primary function within the extruding head 17 to press the rebound material through the grillwork 37. Within the trough 14 the caps 34 add cutting edges to the paddles 32 and scrape encrustations from the wall of the trough 14.

The shaft 26 is also provided at its respective ends with scraper blades 45 which respectively clean the end wall 15 of the trough and end wall 22 of the extruding head 17. Each scraper blade 45 is desirably mounted on a stem 46 and is shiftable thereon by the adjusting bolts 47, thus to insure good scraping contact of the scraper blades 45 with the said end walls.

The output of the rebound pug mill 11 is very much smaller than that of the main pug mill 10. Accordingly, the quantity of fresh material processed by the main pug mill 10 will greatly exceed the amount of rebound material which is returned to the mixer 10 through the rebound pug mill, thus insuring the gradual or metered addition of rebound material and the presence in the output of the main pug mill of only a relatively small proportion of rebound material.

By processing the rebound material in the rebound pug mill, it will be comminuted and extruded into relatively small pieces which will better mix and blend with the fresh material in the main pug mill 10. Thus the material discharged from the main pug mill will be less likely to cause jams or other problems at the molding stations and the ultimate product will be of smooth consistency without hard spots, etc.

lclaim:

1. ln apparatus to reprocess rebound material comprising compacted and de-aerated clay, the combination of a main pug mill for initially mixing fresh materials and a separate rebound pug mill for comminuting rebound material previously processed by the main pug mill and gradually metering comminuted rebound material into the main pug mill for blending with said fresh material, said rebound pug mill having an output materially less than the main pug mill to insure the metered addition of comminuted rebound material into the main pug mill and the presence in the output of the main pug mill of only a relatively small proportion of rebound material, said rebound pug mill comprising a trough with an inlet for rebound material and an extruding head at the end of the trough and having an outlet discharging into the main pug mill, paddles in the trough to comminute rebound material admitted through said inlet and paddles in the extruding head to extrude comminuted rebound material through said discharge outlet and into the main pug mill.

2. The invention of claim 1 in which the discharging outlet in the extruding head comprises an opening in the side of the head and a grill over said opening through which the comminuted material is extruded.

3. The invention of claim 2 in which the extruding head and grill are releasably connected, whereby to facilitate removal of the grill for repair or replacement.

4. The invention of claim 1 in which the extruding head is closed, except for said discharge outlet, thus to build up extruding pressure therewithin.

5. The invention of claim 1 in which said trough and extruding head are releasably connected, whereby to facilitate removal of the extruding head for repair or replacement.

6. The invention of claim 5 in which said releasable connection comprises mating flanges on the trough and extruding head and a row of fasteners releasably connecting said flanges.

7. The invention of claim 1 in which there is a paddle shaft through the trough and extruding head, said paddles in the trough and said paddles in the extruding head being mounted on said shaft.

8. The invention of claim 7 in which the paddles in the trough comprise non-skewed cutting blades extending outwardly from said shaft.

9. The invention of claim 7 in which the paddles in the extruding head have end caps for pressing comminuted rebound material through the grill.

10. The invention of claim 7 in which said paddles are arranged in rows helically wound about said shaft.

11. The invention of claim 7 in which scraper blades are mounted near the ends of the shaft, to clean the adjacent end walls of the trough and extruding head respectively.

12. A mixing method comprising the steps of initially mixing fresh materials in the main pug mill,

returning rebound material previously processed by the main pug mill to a rebound pug mill,

comminuting said rebound material in the rebound pug mill,

discharging said comminuted rebound material from the rebound pug mill into the main pug mill for blending with said fresh material,

and metering the output of the rebound pug mill to materially less than the main pug mill to insure the presence in the output of the main pug mill of only a relatively small proportion of rebound material.

13. The method of claim 12 in which the rebound material is held in a hopper over the rebound pug mill in the course of returning the rebound material to the rebound pug mill.

14. The method of claim 12 in which the step of discharging the rebound material includes extruding it through an extruding head at the discharge end of the rebound pug mill in relatively small pieces.

15. The method of claim 12 in which the fresh materials comprise clay and water, the rebound material comprising such clay and water which has been compacted and deaerated. 

1. In apparatus to reprocess rebound material comprising compacted and de-aerated clay, the combination of a main pug mill for initially mixing fresh materials and a separate rebound pug mill for comminuting rebound material previously processed by the main pug mill and gradually metering comminuted rebound material into the main pug mill for blending with said fresh material, said rebound pug mill having an output materially less than the main pug mill to insure the metered addition of comminuted rebound material into the main pug mill and the presence in the output of the main pug mill of only a relatively small proportion of rebound material, said rebound pug mill comprising a trough with an inlet for rebound material and an extruding head at the end of the trough and having an outlet discharging into the main pug mill, paddles in the trough to comminute rebound material admitted through said inlet and paddles in the extruding head to extrude comminuted rebound material through said discharge outlet and into the main pug mill.
 2. The invention of claim 1 in which the discharging outlet in the extruding head comprises an opening in the side of the head and a grill over said opening through which the comminuted material is extruded.
 3. The invention of claim 2 in which the extruding head and grill are releasably connectEd, whereby to facilitate removal of the grill for repair or replacement.
 4. The invention of claim 1 in which the extruding head is closed, except for said discharge outlet, thus to build up extruding pressure therewithin.
 5. The invention of claim 1 in which said trough and extruding head are releasably connected, whereby to facilitate removal of the extruding head for repair or replacement.
 6. The invention of claim 5 in which said releasable connection comprises mating flanges on the trough and extruding head and a row of fasteners releasably connecting said flanges.
 7. The invention of claim 1 in which there is a paddle shaft through the trough and extruding head, said paddles in the trough and said paddles in the extruding head being mounted on said shaft.
 8. The invention of claim 7 in which the paddles in the trough comprise non-skewed cutting blades extending outwardly from said shaft.
 9. The invention of claim 7 in which the paddles in the extruding head have end caps for pressing comminuted rebound material through the grill.
 10. The invention of claim 7 in which said paddles are arranged in rows helically wound about said shaft.
 11. The invention of claim 7 in which scraper blades are mounted near the ends of the shaft, to clean the adjacent end walls of the trough and extruding head respectively.
 12. A mixing method comprising the steps of initially mixing fresh materials in the main pug mill, returning rebound material previously processed by the main pug mill to a rebound pug mill, comminuting said rebound material in the rebound pug mill, discharging said comminuted rebound material from the rebound pug mill into the main pug mill for blending with said fresh material, and metering the output of the rebound pug mill to materially less than the main pug mill to insure the presence in the output of the main pug mill of only a relatively small proportion of rebound material.
 13. The method of claim 12 in which the rebound material is held in a hopper over the rebound pug mill in the course of returning the rebound material to the rebound pug mill.
 14. The method of claim 12 in which the step of discharging the rebound material includes extruding it through an extruding head at the discharge end of the rebound pug mill in relatively small pieces.
 15. The method of claim 12 in which the fresh materials comprise clay and water, the rebound material comprising such clay and water which has been compacted and de-aerated. 